1.0 General Description

The Model 681 for T1 and the Model 682 for E1 provide T1/E1 line extension, high speed transmission of synchronous data over distances greater than 12,000 feet with an exceptionally high degree of data reliability. This is accomplished by using 2B1Q signaling technology. Available copper transmission media are not ideal. They are bandwidth limited and have non-linear phase characteristics. Nonetheless, the 2B1Q line code reduces many of their deleterious effects and allows signals to be transmitted over much longer distances without repeaters and in the presence of bridge taps. Since no conditioning of transmission lines is necessary when HDSL is used the Model 681/682 represents a plug and play solution for using readily available copper cable pairs for high speed data transmission and Internet access.

When operating as a pair of HDSL Short Haul Modems, the communications link will allow independent digital streams to share two twisted pairs in accordance with the HDSL specification. The Model 681/682 will perform the function of a synchronous short haul modem for full duplex transmission of binary serial data at 1.544 MBPS/2.048 MBPS across two twisted pairs.

2.0 Specifications

2.1 Interface

2.2 Data Rate:
Model 681 - 1.544 MBPS
Model 682 - 2.048 MBPS

2.3 Connectors:
Terminal Interface - DB-25F
Line Interface - RJ-45
Supervisory Interface - DB-9F

2.4 Display: The Model 681/682 is equipped with a LCD display, which is used for device setup and online monitoring. During normal operation, it displays "Modem Setup" and whether it is a HTU-C or HTU-R. The LCD will also indicate if the devices are active.

2.5 Keypad: The Model 681/682 contains a 3 button keypad to allow selection of parameters presented on the display. The keypad allows the user to configure the unit as a HTU-C or a HTU-R, initiate loopbacks and perform noise margin tests.

The operator setup is stored in memory and used as a default setup when the 681/682 is powered up. The setup can be altered at any time and the new setup automatically becomes the new default.

2.6 Diagnostics: The Model 681/682 can be configured to perform two types of loopback - Local and Remote. The Remote loopback will take any data transmitted to the remote unit and loop it back to the local. The Local loopback will perform a local loopback and ignore any data being received from the remote unit. In addition to the loopback modes, the unit has the ability to perform a noise margin test. This will provide a digital representation of the receive signal level.

2.7 Supervisory Port: The Model 681/682 is also equipped with a RS-232 supervisory port that allows the user to configure the device using the LCD or front panel switches. The supervisory port also has the ability to disable the front panel switches preventing changes from being made. Connection via the supervisory port is accomplished by connecting a dumb terminal or a PC that has software that can emulate a dumb terminal or use Hyper Terminal under Windows 95.

2.8 Power: 110 Volts, 60 Hz; 220 Volts, 50 Hz via a wall mounted adapter.

2.9 Operating Temperature: 0° to 50° C, 5 to 95% RH (no condensation)

3.0 Installation

3.1 Digital Interface

The Model 681/682 uses a DB-25 female connector to connect to the external V.35 equipment. The following signals are supported. Adapter cables, CAB 435 (Male v.35 to make DB-25) or CAB 436 (female v.35 to male DB-25) are available as options.

The Model 681/682 is configured as a DCE, i.e. modem. It drives CTS, DSR, and DCD as well as the receive data and receive and transmit clock lines. (RTS and DTR are inputs to the 681/682 that are not used.) The signal voltages are:

3.2 Analog Interface

The HDSL output of the Model 681/682 is terminated with a RJ-45 connector. The pin assignment for the RJ-45 is shown below.

When connecting units 1+ of one unit goes to 1- of the second, 1- to 1+, 2+ to 2-, & 2- to 2+.

3.3 Set Up

The front panel of the Model 681/682 provides three buttons; Menu Scroll, Select, and Load. "Menu Scroll" allows you to move between 2 different options - HTU-C/R and loopback selection. "Select" allows the user to toggle between the different possibilities. After all selections have been made the "Load" button will save the settings and reinitialize the unit. The default setting for each unit is HTU-C and Normal. When connecting a link of two units, one must be set as an HTU-C and the other as an HTU-R.

To setup and configure the Models 681/682 perform the following steps.

1. Connect the two twisted pair lines to the unit via the RJ-45 connector - one twisted pair should be connected to pins 3 and 6 of this connector, the other between 4 and 5. Note: The four wire line between modems must be two twisted pairs. On each modem, the wires marked 1+ and 1- must be members of the same twisted pair, 2+ and 2- members of the other.

2. Connect the V35 cable.

3. Insert power jack and connect the wall transformer to the buildings power. Note that the LCD becomes active. It should display "Power up" momentarily, then "configuring system" for less than 60 seconds. During this latter period, the character at the beginning of the second line should rapidly change.

4. When the display changes to "Telebyte Technology", press the Menu Scroll button.

5. Depress the Select until the LCD displays "HTU-C", for the remote unit select "HTU-R"

6. Depress the Menu Scroll button again.

7. Depress the Select until the LCD displays "Normal"

8. Depress the Load button. The display should change to starting link and progress through all the starting stages. When the test is successful, the display will end with "Linked" and the two units are ready to transmit data.

The supervisory port is implemented as a DTE interface, pin 3 is data out of the box, pin 2 is data in and pin 5 is ground.

To perform these steps using the supervisory port, connect a dumb terminal to the rear mounted DB-9 connectors. The terminal is to be setup for operation with 8 bits, no parity, at 1200 baud. Depressing the return key will activate a menu that duplicates the front panel.

3.4 Loopbacks

The Model 681/682 can be configured for two different loopback configurations "Local" and "Remote".

The "Local" refers to the front-end analog circuitry that is between the HDSL recovery logic and the HDSL twisted pair. "Local" loopback provides a self-test mode where a single Model 681/682 takes V35 data, transmits it, receives its own transmission, and delivers it to the V35 receive data pin. In this mode, the transmit path is unchanged and the input to the receive path is switched from the twisted-pair to the transmit output.

The "Remote" refers to the V35 interface. "Remote" loopback provides a method of testing a complete pair of 68X's when one 68X is operating normally and the other is in loopback. In this configuration, the data is taken from the normal unit's V35 transmit data line, sent on the twisted pair, received by the loopback unit, decoded and presented on the loopback unit's V35 receive line. This receive line is also loopbacked to the V35 transmit input. So the data is then encoded a second time and echoed back to the normal originating unit where it ultimately appears on its V35 receive data line.

To enable loopbacks press the Menu Scroll button twice and then use the Select button to choose which loopback is required. Then press the Load to initiate the loopback. The front panel display will then show that the unit is loopback and will begin going through its initialization steps to link to itself. Then return the unit back to its normal operation mode by pressing the Menu Scroll button twice and then use the Select button to choose Normal. Then press the Load and the unit will then begin its normal initialization steps to link to the remote unit.

4.0 Front Panel Display

During Normal operation, the top line of the LCD displays "Telebyte Technology HTU-X". When the units are configured for a loopback test the word "Telebyte Technology" is replaced with "Local Loopback" or "Remote Loopback".

The second line of the display contains the status of the "worst channel". During start-up, this line contains an indication of the various adaptations automatically occurring inside the modem. When the connection is first made, this line changes to "active." After 30 seconds, it reaches its operating state of "linked." Should the line be broken or other malfunction occur, the status will be "Inactive".

The two numbers on the left of the second line, indicate the signal quality on each twisted pair. The numbers range from 8 for very minimal quality to 48 for perfect connection.

5.0 Troubleshooting

The following is a list of possible problems that may arise during the installation:

1. No display.
a) Check power connections
b) Defective unit.

2. "Configuring System" does not appear at startup or letter on the second line does not change.
a) Defective unit.

3. Unit fails "Local" loopback test.
a) Speed of user equipment is not at 1.544MBPS (or 2.048MBPS for the Model 682).

4. Unit fails normal operation.
a) Defective twisted pair connection. Verify that the RJ connector has been properly wired.
b) Exceeded maximum distance or poor quality line

6.0 Power

The Model 681/682 is powered by a small, wall mounted power cube that supplies 12 VDC @ 500 mA. NOTE: The power supply must be connected to the Model 681/682, through the 1.3mm connector located on the rear of the unit, prior to plugging the power supply into the wall.

7.0 Help

If any assistance is required call Bomara Associates at (800)-5BOMARA or (978)-452-2299.
Technical Support E-Mail: bobr@bomara.com
or use our Online Contact Form

Document No. 0315-0252
Rev. A

Warranty

Telebyte warrants the equipment to be free from defects in material and workmanship, under normal and proper use and in its unmodified condition, for 12 months, starting on the date it is delivered for use. TELEBYTE's sole obligation under this warranty shall be to furnish parts and labor for the repair or replacement of products found by TELEBYTE to be defective in material or workmanship during the warranty period. Warranty repairs will be performed at the point of manufacture. Equipment approved for return for warranty service shall be returned F.O.B. TELEBYTE factory and will be redelivered by TELEBYTE freight prepaid, except for non- continental U.S.A. locations. These deliveries will be sent COD freight and import/export charges.

THE ABOVE WARRANTY IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESSED OR IMPLIED, STATUTORY OR OTHERWISE, INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. TELEBYTE SHALL NOT BE LIABLE FOR ANY DAMAGES SUSTAINED BY RESELLER OR ANY OTHER PARTY ARISING FROM OR RELATING TO ANY EQUIPMENT FAILURE, INCLUDING, BUT NOT LIMITED TO CONSEQUENTIAL DAMAGES NOR SHALL TELEBYTE HAVE ANY LIABILITY FOR DELAYS IN REPLACEMENT OR REPAIR OF EQUIPMENT.

Out of warranty equipment may be returned to the Greenlawn, NY customer service facility prepaid as described above. Return shipping charges will be billed to the customer. The repaired unit will have a 90 day warranty. In those cases where "NO TROUBLE" is found, a reduced charge will be billed to cover handling, testing and packaging.